JP6425439B2 - Water absorption sheet - Google Patents

Description

  The present invention relates to a water absorbent sheet.

  In pads used in medical and sanitary materials, cotton containing a water absorbing polymer, a sheet containing a water absorbing polymer, and a water absorbing foam are used. As the water absorption pad, water absorption speed, water absorption amount, Rewet property, etc. are required.

  Here, a foam (open-cell foam) having pores communicated with the inside can be mentioned as a material having particularly water absorbability.

For example, Patent Document 1 and Patent Document 2 disclose a water-absorbent polyurethane foam obtained by gelling and crosslinking a polyurethane water dispersion in the presence of a water-soluble polyisocyanate compound and an amine compound. .
In addition, Patent Document 3 proposes a foam comprising a water-insoluble cellulose-based water-absorbing polymer in combination with a polymer water dispersion and containing a cellulose-based water-absorbing polymer in its structure.

  Furthermore, as a method of improving the water absorbency of the foam, Patent Document 4 discloses that the obtained foam is impregnated with a surfactant or an aqueous solution containing a water absorbing polymer, and the surfactant is attached to the entire surface of the foam. Proposed.

  As a water absorbing material other than the above-mentioned foam, SAP (super water absorbing resin) is mentioned. For example, Patent Document 5 discloses a composite sheet in which an SAP supporting layer which is a water absorbing layer and a hydrophilic absorbing diffusion layer (for example, a sheet or a non-woven fabric) laminated on the SAP supporting layer are combined. There is. Patent Document 6 discloses a water-absorbent material in which a urethane resin foam is laminated on an SAP sheet via an adhesive.

Japanese Patent Application Laid-Open No. 2003-48940 Japanese Patent Application Publication No. 2006-328288 Japanese Patent Application Laid-Open No. 3-177440 JP 2011-256302 A Patent document 1: JP 2008-136583 International Publication WO 2013/180937

  However, although the foams described in Patent Documents 1 to 4 show water absorbency, they are insufficient in the function of retaining the absorbed water, have high Rewet properties, and can be applied as medical and hygiene materials. It was difficult. Moreover, according to the composite sheet described in Patent Document 5, it was possible to make the absorption capacity of the SAP support layer efficient to some extent, but with the sheet or nonwoven fabric disclosed in Patent Document 5, etc. And the function as a water absorption / diffusion layer was not sufficient (so that the absorption capacity of the SAP support layer was not fully utilized). Furthermore, although the water absorbing material described in Patent Document 6 is also superior in Rewet prevention performance (lower in Rewet property) than when the foam alone is used, etc., when the water absorption speed or Rewet prevention performance is insufficient. There was room for improvement, etc.

  Then, an object of the present invention is to provide a water absorption sheet which has a high water absorption speed and a high liquid holding power (excellent in rewet prevention performance).

Means for Solving the Invention

  As a result of intensive studies to solve the above problems, the present inventors made a water absorbent sheet having a layer structure having a specific foam and a layer containing a super absorbent resin (SAP). It has been found that a water-absorbent sheet having excellent water absorption performance (water absorption speed and liquid retention) can be obtained, and the present invention has been completed.

That is, the present invention (1) is
A water-absorbent sheet comprising a water-absorbent resin foam layer and a highly water-absorbent resin (SAP) layer,
The water-absorbent resin foam layer is
An aqueous system comprising a water dispersible resin as a dispersoid, an anionic surfactant as a foaming agent, water or a mixture of water and a water-soluble solvent as a dispersion medium, and a water-soluble polymer soluble in the dispersion medium A gas is mixed into the liquid medium and stirred to foam the aqueous liquid medium to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated to evaporate the dispersion medium, thereby forming a water absorbent resin foam. It is a water-absorbent sheet that is the body.
The present invention (2) is
It is a water absorbing sheet of said (1) in which the said highly water absorbent resin (SAP) layer and the said water absorbent resin foam layer are laminated | stacked in this order directly or via another layer.
The present invention (3) is
The water absorbing sheet further comprises a water impermeable layer,
The water impermeable layer is a layer directly or separately from the side of the superabsorbent resin (SAP) layer opposite to the side laminated directly or through another layer with the water absorbent resin foam layer. It is a water absorption sheet of the above (2) which is laminated via.
The present invention (4) is
(3) The water-absorbent sheet according to (3), wherein the other layer and / or the another layer is a water-permeable sheet covering the superabsorbent resin (SAP).
The present invention (5) is
The water absorbent resin foam is
It is a water absorbing sheet in any one of said (1)-(4) obtained by the method including the thixotropy provision process which reduces the fluidity | liquidity of the said foaming aqueous liquid medium after the said foaming.

  Here, in the present invention, "water impermeable" means that liquid water does not permeate, and water vapor may or may not permeate. "Water-permeable" means that liquid water can permeate. The term "water absorbency" broadly indicates the property of absorbing water (liquid), and can be evaluated by the water absorption rate, the water absorption rate, the water absorption amount, and the like. Also, "layer" indicates that a member (material) exists continuously in a certain direction, but is generally discontinuous if it can be recognized as a layer. (For example, it may be island-like or dot-like).

  According to the present invention, it is possible to provide a water-absorbent sheet having a high water absorption speed and a high liquid holding power (excellent in the rewet prevention performance).

It is a conceptual sectional view of a water absorption sheet concerning this form. It is a conceptual sectional view of a water absorption sheet concerning this form. It is a section SEM photograph of the resin foam concerning a reference example 2-1. It is a cross-sectional SEM photograph of the resin foam concerning reference example 2-19. It is a section SEM photograph of the resin foam concerning a reference comparative example 2-1. It is a figure which shows the calculation method of the cell diameter of the resin foam based on the reference example 2-1. It is a figure which shows the calculation method of the cell diameter of the resin foam based on the reference example 2-1. It is a figure which shows the calculation method of the cell diameter of the resin foam based on the reference example 2-1. It is a figure which shows the calculation method of the cell diameter of the resin foam based on the reference example 2-1. It is a figure which shows the calculation method of the cell diameter of the resin foam based on the reference example 2-1.

  Hereinafter, although the suitable embodiment of the present invention is described in detail, these are examples to the last, and the present invention is not limited to the following modes.

The water absorbent resin foam according to the present embodiment and the method for producing the same will be described in the following order.
1 Structure of water-absorbent sheet 2 Method of manufacturing water-absorbent sheet 3 Properties of water-absorbent sheet 4 Applications of water-absorbent sheet

[Construction]
FIG. 1 is a conceptual cross-sectional view of a water absorbent sheet 100. As shown in FIG. As shown in FIG. 1, the water absorbing sheet 100 according to the present embodiment includes a water absorbing resin foam layer 110 (hereinafter also referred to as a water absorbing resin foam 110, a resin foam 110, etc.) and a water absorbing resin foam. And a SAP layer 120 below the body layer 110. Further, a water impermeable layer 130 is provided further below the SAP layer 120, and water permeable layers 140 are provided on the upper and lower surfaces of the SAP layer. In addition, as the water absorbing sheet 100 according to the present embodiment, it is sufficient that the water absorbent resin foam layer 110 and the SAP layer 120 are essentially included, and as shown in FIG. The laminated structure can be changed as appropriate, such as not having it.

  Hereinafter, the water-absorbent resin foam layer 110 and the SAP layer 120 will be described, and then the other layers (water-impermeable layer 130 and water-permeable layer 140) will be described. In the present embodiment, in the above-described laminated structure, the water-absorbent resin foam layer 110, which is a layer to which water can contact first at the time of use, is the “upper layer” side, and then water moves The water impermeable layer 130 which is the opposite side) is the “lower layer” side. Further, the movement of water from the upper layer side to the lower layer side is referred to as “flowing down” of water.

«Water-absorbent resin foam»
The water-absorbent resin foam 110 according to the present embodiment is a layer provided as an upper layer of the SAP layer 120, and functions as a dispersion layer for dispersing the water flowing down to the SAP layer 120. More specifically, after the water in contact with the water absorbent resin foam 110 is absorbed by the water absorbent resin foam, it passes through the cells inside the water absorbent resin foam 110, and the water absorbent resin foam 110 Move from the upper layer side to the lower layer side and are led to the SAP layer 120 which is a water holding layer.

  Here, the water-absorbent resin foam 110 according to the present embodiment is a water-dispersible resin as a dispersoid, an anionic surfactant as a foaming agent, water as a dispersion medium, or a mixture of water and a water-soluble solvent. A gas is mixed with an aqueous liquid medium containing a water-soluble polymer dissolved in the dispersion medium and stirred to foam the aqueous liquid medium to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated. It is a water-absorbent resin foam obtained by evaporating the dispersion medium (a specific manufacturing method of the water-absorbent resin foam 110 will be described later).

  According to the water-absorbent resin foam 110 according to the present embodiment, the foam is formed in such a manner that the water-soluble polymer penetrates into the interior of the foam and into the matrix, so that water absorption is exhibited over the entire interior of the cell to absorb water. It becomes excellent in force (water absorption speed). More specifically, as a result of the hydrophilicity being exhibited to the inside of the cell, the dispersion of the water between the cells inside the foam is promoted, and the water can be dispersed in a wide range. Therefore, when the water comes in contact with the SAP layer 120 present in the lower layer of the water-absorbent resin foam 110, the water is dispersed widely, and the SAP of the wider surface comes in contact with the same amount of water. It is possible to prevent water saturation in the SAP layer 120 and to improve water retention. Furthermore, it is possible to rapidly introduce moisture to the water retention layer, the SAP layer 120, by such high water absorption. Since the time in which the water is present in the water absorbent resin foam 110 having a low water holding capacity is shortened, rewet hardly occurs. Furthermore, since the water-soluble polymer is partially embedded in the polymer matrix, it becomes difficult for the water-soluble polymer contained in the water-absorbent resin foam 110 to fall off (the resin is excellent in repeat resistance). Therefore, even when a large amount of water flows down, the water-soluble polymer is unlikely to drop off halfway, so long-term water absorbability can be exhibited.

<Thickness>
As thickness of the resin foam 110 which concerns on this form, although it can design suitably according to a use, it is suitable that they are 0.3 mm-3.0 mm.

<Cell structure>
The resin foam 110 according to this embodiment is preferably a hole-in-hole foam. With such a structure, the holes present in the membrane of each cell exert a capillary phenomenon to exhibit the effect of improving the water absorption (as a result, the effect of the above-mentioned dispersibility is more strongly exhibited. ). More specifically, the resin foam 110 according to the present embodiment is excellent in the dispersibility of water between adjacent cells inside the foam, but by being a hole-in-hole type, The capillary phenomenon is exhibited also in the provided opening, and the dispersibility is further improved. In the "hole-in-hole type foam", in each cell of the foam, a plurality of holes (openings) having a diameter smaller than the cell diameter of the cell are present in the membrane portion corresponding to the wall surface of the cell. It is a foam.

(Average cell diameter)
The average cell diameter (average cross-sectional cell diameter) of the cross section of the resin foam 110 is preferably 5 μm or more (for example, 10 μm or more) 300 μm or less, more preferably 5 μm or more and 200 μm or less, and 5 μm or more and 100 μm or less Is particularly preferred. In addition, as a measuring method of an average cell diameter, it shall follow the following method.

  First, a cell photograph of a cross section of the resin foam 110 is taken using a scanning electron microscope (SEM, VHXD-500 manufactured by Keyence Corporation). Thereafter, each cell diameter is measured using image processing software Image-Pro PLUS (6.3 ver, manufactured by Media Cybernetics). More specifically, the SEM image is read, and the contrast is adjusted in order to recognize the cells in the contrast. Next, the shape of the cell is read by image processing (it is not a perfect circle but the shape is recognized as it is). Next, "diameter (average)" is selected as a measurement item. Next, each cell diameter is calculated as a value obtained by measuring the diameter passing through the center of gravity of the object in steps of 2 degrees and averaging them.

(Distribution of cell diameter)
In the cross-sectional cell photograph, regarding each cell in the cross section of the foam, Sx / S ≧ in the total value S of the cell cross-sectional areas of all the cells and the total value Sx of the cell areas whose cross-sectional cell diameter is 1 to 100 μm It is preferred that the ratio is 0.1, more preferably Sx / S ≧ 0.2, and particularly preferably Sx / S ≧ 0.3. The upper limit value of Sx / S is not particularly limited, and is, for example, 1. More preferably, it is preferable that Sy / S ≧ 0.05 in the total value S of the cell cross-sectional areas of all the cells and the total value Sy of the cell areas having a cross-sectional cell diameter of 50 to 125 μm. It is more preferable that Sy / S ≧ 0.1, and it is particularly preferable that Sy / S ≧ 0.15. The upper limit value of Sy / S is not particularly limited, but for example, by setting the cross-sectional cell diameter and the distribution of cross-sectional cell diameter to 1 in such a range, it is possible to expect more water absorption due to the capillary phenomenon (the As a result, the effect of the dispersibility is more strongly exhibited).

<Material>
The material (material) of the resin foam 110 will be described in detail in the manufacturing method described later.

<< SAP layer >>
The SAP layer 120 functions as a water retention layer that holds the water flowing into the water absorbent sheet 100 so as not to be rewetted. In addition, SAP is Super Absorbent Polymer and is a super absorbent resin.

  It is not limited at all as SAP which is a component of SAP layer 120 concerning this form, and it is possible to use SAP of known composition and form, for example, carboxymethylcellulose, polyacrylic acid, sodium polyacrylate, etc. Crosslinked acrylate polymer, copolymer of starch and acrylic acid graft, hydrolyzate of starch and acrylonitrile graft copolymer, crosslinked polyoxyethylene, crosslinked carboxymethylcellulose, polysulfonic acid compound, polyethylene A polymer obtained by partially crosslinking a water-swellable polymer such as oxide or polyacrylamide, a copolymer of isobutylene and maleic anhydride, or a saponified product thereof, etc. may be mentioned. Further, the shape of SAP contained in the SAP layer 120 is not limited in any way, such as particulate, granular, fibrous, film or non-woven.

  The SAP layer 120 is not a layer consisting only of SAP (for example, a layer in which fibrous or film-like SAPs are directly disposed), but a layer in which particulate, granular or fibrous SAP is substantially fixed to a non-woven fabric or the like. Other materials may be included. That is, SAP layer 120 should just be formed as a layer containing SAP by a publicly known method (for example, the below-mentioned SAP carrying sheet etc. can be used suitably).

<SAP amount>
The amount of SAP in the SAP layer 120 according to the present embodiment (for example, the amount of particulate SAP carried on the non-woven fabric) can be appropriately designed depending on the application, but 1000 to 5000 g / m ² (0.9% It is preferable that the water absorption amount of the sodium chloride aqueous solution be obtained (in this case, the thickness of the SAP layer 120 and the like may be appropriately designed in accordance with the SAP shape and the SAP amount).

«Other layers»
As mentioned above, the layer laminated | stacked other than the water absorbing resin foam layer 110 and SAP layer 120 is demonstrated as a water absorbing sheet 100 which concerns on this form.

<Water impermeable layer>
It is preferable to provide the water impermeable layer 130 below the SAP layer 120. With such a configuration, the water which has flowed down from the upper layer (SAP layer side) of the water impermeable layer 130 is provided to block the water and keep the water in the SAP layer 120. Water leakage to the lower layer side is prevented (wetting is less likely to occur on the side opposite to the side on which the water comes in contact). Therefore, the water retention of the whole water absorbing sheet 100 improves. Furthermore, by providing the water impermeable layer 130 in the lower layer of the SAP layer 120, it is possible to prevent the falling off of the SAP in the SAP layer 120 (the outflow from the water absorbent sheet 100) and to exhibit high water retention over a longer time. It becomes.

<Thickness>
The thickness of the water impermeable layer 130 can be appropriately designed depending on the application, but is preferably 4 μm to 38 μm. If it is 4 μm or less, there is a problem of lack of strength, and if it is 38 μm or more, it is nonconforming (hard) because it loses its flexibility at the end use. If it is this thickness, while it has the strength as a water absorption sheet, the strength as a carrier at the time of manufacture is also secured, and it is suitable also for use.

<Material>
Such a water impermeable layer 130 is not particularly limited, and for example, a film of a polymer material such as polyester (eg, PET etc.), polyolefin (eg polyethylene, polypropylene etc.), polyurethane, polycarbonate, polyamide etc. Although it is good, it is preferable that it is PET.

«Water permeable layer»
In addition to the above, as the laminated structure of the water absorbing sheet 100, the water permeable layer 140 may be further included as the outermost layer or the intermediate layer in the range not to prevent the flow of water.

  For example, the water absorbing sheet 100 according to the present embodiment has the water permeable layer 140 as the upper layer and the lower layer of the SAP layer 120. As described above, by configuring the water permeable layer 140 to support the SAP layer 120, the shape retention of the SAP layer 120 can be enhanced. More specifically, the presence of the water-permeable layer 140 in the lower layer of the SAP layer 120 can prevent the SAP from falling off (the outflow from the water absorbent sheet 100) in the SAP layer 120. Furthermore, for example, when the foamed resin layer 110 is cast on the SAP layer 120 in the manufacturing stage, the water-permeable layer 140 is provided on the SAP layer 120, and the foamed resin layer 110 is cast thereon. , Suppressing the SAP movement and forming a uniform SAP layer (the casting of the foamed resin layer 110 will be described later). In this case, a single SAP carrying sheet is formed by the water permeable layer 140 and the SAP layer 120 (the SAP carrying sheet will be described later).

<Material>
The water-permeable layer 140 is not particularly limited as long as it has water permeability, but a fiber sheet (woven fabric or non-woven fabric) such as natural fiber, compound fiber, wood pulp, paper, etc. may be used. In addition, as the non-woven fabric, one processed by a known method such as a card web method, a needle punching method, a spun lace method, a web folding method and the like may be used.

<Thickness>
The thickness of the water-permeable layer 140 according to the present embodiment is not limited at all, and can be appropriately designed in a range having water permeability according to the material and the like.

Incidentally, the nonwoven fabric as a water permeable layer 140 according to the present embodiment (e.g., tissue) in the like case of using, as its basis weight, it is preferable that a ^{5g / m 2 ~100g / m 2} .

[Production method]
The water absorbing sheet 100 according to the present embodiment is a laminate formed by laminating a plurality of layers. The method for producing the water-absorbent resin foam 110 (lamination method) is not particularly limited, but after a base (SAP carrying sheet) having the SAP layer 120 supported on the water permeable sheet 140 is formed, Preferably, the water-absorbent resin foam 110 is cast and cured. By thus directly casting the water-absorbent resin foam 110 on another layer, the adhesion between the layers can be enhanced without using an adhesive or the like (as a result, from the water-absorbent resin foam 110, The flow of water to the SAP layer 120 is smoothly performed).

  As a method of producing the water-absorbent resin foam 110 (lamination method), in addition, a plurality of sheet-like layers (sheet-like water-absorbent resin foam 110, SAP carrying sheet carrying SAP layer 120, etc. Layers may be laminated in a desired order, and they may be laminated by bonding them together with an adhesive or the like as appropriate and integrating them.

  When the integration of a plurality of layers (in particular, the integration of the water absorbent resin foam 110 to the SAP layer 120) is performed using an adhesive or the like, the water absorbent resin foam 110 which is a water dispersion layer is used. In order not to inhibit the flow of water to the water retention layer, that is, the SAP layer 120, it is desirable that the dots be partially adhered, for example, by providing an adhesive. Such a configuration makes it difficult to inhibit the flow of water.

  In addition, as a method of manufacturing the water-absorbent resin foam 110 (lamination method), after the water-absorbent resin foam 110 is formed in advance, a dispersed slurry containing SAP, etc. is foamed with the water-absorbent resin directly or through another layer. It may be applied on the body 110 to form the SAP layer 120, and so on.

  Next, after a detailed method of adjusting the water-absorbent resin foam 110 is described in detail, a base material (SAP carrying sheet) having the SAP layer 120 supported on the water permeable sheet 140, which is a preferred form of the SAP layer 120. The adjustment method of will be described.

«Method of adjusting water-absorbent resin foam»
In the method of preparing the water-absorbent resin foam 110 according to the present embodiment, a water-dispersible resin as a dispersoid, an anionic surfactant as a foaming agent, water as a dispersion medium, and a water-soluble polymer dissolved in the dispersion medium The aqueous liquid medium containing and mixed with gas is caused to foam so that the aqueous liquid medium is foamed to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated to evaporate the dispersion medium to produce a resin foam And a water-soluble polymer which is soluble in the dispersion medium as a raw material. As a method of adjusting the water-absorbent resin foam 110, the raw material, the composition (the compounding amount), and the process (a specific adjustment step) will be described in detail.

  In addition, in the adjustment method of the water absorbent resin foam 110 which concerns on this form, in order to prevent the unification of the bubble in a foaming aqueous liquid medium, the thixotropy provision process which reduces the fluidity | liquidity of the said aqueous liquid medium is included. Here, the thixotropy-imparting step may be a known means, but in an aqueous liquid medium (foamed aqueous liquid medium), not only anionic surfactants (foaming anionic surfactants), but also systems The anionic surfactant (A) present in (1) may be insolubilized in some form in the dispersion medium. More specifically, it may be a step of insolubilizing the foaming anionic surfactant dissolved in the dispersion medium in the dispersion medium. Hereinafter, the case where the foaming anionic surfactant dissolved in the dispersion medium is insolubilized with respect to the dispersion medium is referred to as “insolubilization of anionic surfactant”, “insolubilization step”, and the like.

<Raw material>
The resin foam 110 according to the present embodiment is, as a raw material, a water dispersible resin, an anionic surfactant, water as a dispersion medium, a water soluble polymer, a water soluble polymer crosslinking agent, a gelling component (gelling agent) and other Additives and the like (note that the foaming gas used in the foaming process will be described in the foaming process). In the present invention, the water dispersible resin may be a water dispersion in which the resin is dispersed in water.

(Water-dispersible resin)
The adjustment method of the resin foam 110 which concerns on this form contains water dispersible resin as a main ingredient. The water dispersible resin is not particularly limited in its structure or adjustment method, and any water dispersible resin may be used.

  Here, when the water-dispersible resin according to the present embodiment insolubilizes the anionic surfactant, the suitable utilization form differs depending on whether it is a stable dispersion type or an unstable dispersion type. Next, each of the stable dispersion type water dispersible resin and the unstable dispersion type water dispersible resin will be described in detail. In addition, the water dispersible resin of stable dispersion type is a water dispersible resin of which the precipitation rate (the specific calculation method of the precipitation rate follows the following method) is less than 10%, unstable dispersion type water dispersibility The resin means a water dispersible resin having a deposition rate of 10% or more.

Method of calculating precipitation rate In order to evaluate the dispersion stability of the water-dispersible resin, an aqueous coagulant solution (0.5 mass% calcium nitrate aqueous solution) is added to the water-dispersible resin, and the amount of precipitates formed The deposition rate was calculated. The specific precipitation rate is determined by the following formula (1) {In addition, in the formula (1), A is the dry mass (g) of the precipitate, B is the mass (g) of the water dispersible resin, and C is the water dispersion Solid concentration (mass%) of the water-soluble resin}.
Precipitation rate (%) = A / {B × (C / 100)} × 100 (1)

  More specifically, in a room at 23 ° C., 10 g of a water-dispersible resin is put in a resin container having a volume of 100 ml, and while stirring, 10 g of a calcium nitrate aqueous solution having a concentration of 0.5 mass% is dropped as a coagulant aqueous solution. After dropping the whole amount of the coagulant aqueous solution, it is allowed to stand for 1 hour. Next, all of the glass filter (manufactured by Shibata Scientific Co., Ltd., suction filtration bottle 1 L, manufactured by Shibata Scientific Co., Ltd., for glass filter base φ 47 mm, manufactured by Kazan Seisakusho Co., Ltd., Kazan Separoto 55Z) and 40 mesh filter (Yamani Co., Ltd.) Product, T230LY-40), and filtered under reduced pressure to recover a precipitate. Further, the filtrate is washed with water until it becomes clear and then dried at 110 ° C. for 3 hours. The dry mass of the precipitate is measured, the deposition rate is calculated based on the formula (1), and the dispersion stability of the water-dispersible resin is evaluated from the deposition rate. That is, since a thing with a precipitation rate of less than 10% means that resin particles are hard to aggregate, it is evaluated as a "stable dispersion type water dispersible resin", and a thing with a precipitation rate of 10% or more is an aggregation of resin particles. It is evaluated as "unstable dispersion type water dispersible resin" to mean that it is easy to do.

  In addition, as a water dispersible resin which concerns on this form, it is not limited to one type of water dispersible resin, You may use it combining multiple types of water dispersible resin. As described above, even when the water dispersible resin is composed of a plurality of water dispersible resins, the precipitation rate is calculated in the entire water dispersible resin, and whether it is a stable dispersion type or an unstable dispersion type, To determine

Stable Dispersion-Type Water-Dispersible Resin The stable dispersion-type water-dispersible resin is not particularly limited, and examples thereof include a urethane emulsion, an acrylic emulsion, a vinyl acetate emulsion, a vinyl chloride emulsion, and an epoxy emulsion. Of these, particularly preferred urethane emulsions and acrylic emulsions are described in detail. The use of the urethane emulsion is preferable because the flexibility of the resulting urethane resin foam is excellent and the compressive residual strain is low. In addition, it is also preferable to use an acrylic emulsion because it is excellent in strength, lightness and heat insulation.

The following method (I)-(III) can be illustrated as a preparation method of the water dispersion (urethane emulsion) of a urethane resin.
(I) An organic solvent solution or an organic solvent dispersion of a urethane resin having a hydrophilic group obtained by reacting an active hydrogen-containing compound, a compound having a hydrophilic group, and a polyisocyanate, as necessary, neutralization A method of mixing an aqueous solution containing an agent to obtain a urethane resin water dispersion.
(II) An active hydrogen-containing compound, a compound having a hydrophilic group, and a terminal isocyanate group-containing urethane prepolymer having a hydrophilic group obtained by reacting a polyisocyanate are mixed with an aqueous solution containing a neutralizing agent Alternatively, after a neutralizing agent is added to the prepolymer in advance, water is mixed and dispersed in water, and then reacted with a polyamine to obtain a urethane resin water dispersion.
(III) A compound having an active hydrogen-containing compound, a compound having a hydrophilic group, and a terminal isocyanate group-containing urethane prepolymer having a hydrophilic group obtained by reacting a polyisocyanate, mixed with an aqueous solution containing a neutralizing agent and a polyamine Alternatively, after adding a neutralizing agent to the prepolymer in advance, an aqueous solution containing a polyamine is added and mixed to obtain a urethane resin water dispersion.

  Examples of the polyisocyanate used in the preparation of the urethane resin include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4 '-Diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro- 4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate Dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4 Examples thereof include '-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate and the like. Moreover, in the range which does not impair the effect of invention, you may use together the polyisocyanate more than trivalence.

  Further, examples of the compound having a hydrophilic group include polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyacrylate polyols, polyesteramide polyols, polythioether polyols, and polyolefin polyols such as polybutadiene. These high molecular weight compounds may be used in combination of two or more. Known polyester polyols may be used.

  In the above methods (I) to (III), an emulsifying agent may be further used as long as the effects of the invention are not impaired. Such emulsifiers include, for example, nonionic emulsifiers such as polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene sorbitol tetraoleate; fatty acid salts such as sodium oleate, alkyl Anionic emulsifier such as sulfuric ester, alkyl benzene sulfonate, alkyl sulfo succinate, naphthalene sulfonate, alkane sulfonate sodium salt, alkyl diphenyl ether sulfonate sodium salt; polyoxyethylene alkyl sulfate, polyoxyethylene alkyl phenyl sulfate Etc. can be exemplified.

  As a process for producing a water dispersion of acrylic resin (acrylic emulsion), a polymerizable unit amount of (meth) acrylic acid ester monomer is required in the presence of a polymerization initiator, and, if necessary, an emulsifier and a dispersion stabilizer. It can be obtained by copolymerizing a mixture of other polymerizable monomers copolymerizable with these monomers as a body component, if necessary.

  Examples of the polymerizable monomer that can be used to adjust the above acrylic resin emulsion include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) arrylate (meth) ) Hexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, octadecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, nonyl (meth) acrylate ( (Meth) acrylic acid such as dodecyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate Ester-based monomer; acrylic acid, methacrylic acid, β-carboxyethyl Unsaturated having carboxyl group such as meta) acrylate, 2- (meth) acryloyl propionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid half ester, maleic acid half ester, maleic anhydride, itaconic anhydride etc. Bond-containing monomer; Glycidyl group-containing polymerizable monomer such as glycidyl (meth) acrylate, allyl glycidyl ether; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) Hydroxyl group-containing polymerizable monomers such as acrylate and glycerol mono (meth) acrylate; ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and trimethyl Examples include roll propane tri (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, diallyl phthalate, divinyl benzene, allyl (meth) acrylate and the like.

  In addition, when using an emulsifier at the time of adjustment of an acrylic emulsion, the above-mentioned emulsifier etc. may be used.

Unstable dispersion type water dispersible resin The unstable dispersion type water dispersible resin is not particularly limited, and rubber latex etc. can be exemplified. The rubber latex is preferable because the feel of the foam is good and the elasticity is excellent. Next, the rubber latex will be described in detail.

  The water dispersion (rubber latex) of the rubber according to the present embodiment may be a natural rubber latex or a synthetic rubber latex. The synthetic rubber latex can be obtained by emulsion polymerization of an aliphatic conjugated diene-based monomer and another copolymerizable polymerizable monomer. Here, as an aliphatic conjugated diene type monomer, a 1, 2- butadiene, a 1, 3- butadiene, an isoprene, a chloroprene etc. can be illustrated.

  As another polymerizable monomer which can be copolymerized, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) arylate, hexyl (meth) acrylate ( (Meth) acrylic acid ester monomers such as heptyl acrylic acid, octyl (meth) acrylic acid, octadecyl (meth) acrylic acid; (meth) acrylic acid, crotonic acid, maleic acid and its anhydride, fumaric acid , Unsaturated bond-containing monomers having a carboxyl group such as itaconic acid, unsaturated dicarboxylic acid monoalkyl esters (eg monomethyl maleate, monoethyl fumarate, mononormal butyl itaconate); styrene, α-methylstyrene, vinyl toluene Ethylenically unsaturated aromatic monomers such as chlorostyrene and 2,4-dibromostyrene; Unsaturated nitriles such as ryronitrile and methacronitrile; vinyl esters such as vinyl acetate and vinyl propionate; vinylidene halides such as vinylidene chloride vinylidene bromide; 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid-2 Hydroxyalkyl esters of ethylenically unsaturated carboxylic acids such as hydroxypropyl; glycidyl esters of ethylenically unsaturated carboxylic acids such as glycidyl (meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, butoxymethyl (meth) ) Acrylamide, diacetone acrylamide and the like can be exemplified.

  A rubber latex (synthetic rubber latex) that can be used as a water-dispersible resin can be obtained by emulsion polymerization of the above-mentioned monomers in an aqueous medium in the presence of an emulsifier, a free radical generating catalyst, and the like. At this time, a two-stage polymerization method can also be adopted. As the emulsifier, various anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants and the like can be used.

  Incidentally, in the classification according to the unstable dispersion type or the stable dispersion type of the water dispersible resin of the present embodiment, the classification according to the above-mentioned materials is schematic {the water dispersible resin is the unstable dispersion type or the stable dispersion Whether it is a type is, to the last, classified by the above-mentioned formula (1)}. For example, a urethane emulsion having a precipitation rate of 10% or more in the above formula (1) is classified as an unstable dispersion type water-dispersible resin, and a rubber latex having a precipitation rate of less than 10% is a stable dispersion type. Water dispersible resin.

(Dispersion medium)
In the present embodiment, as a dispersion medium of the aqueous liquid medium, water is an essential component, but a mixture of water and a water-soluble solvent may be used. The water-soluble solvent is, for example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, butyl cellosolve, polar solvents such as N-methylpyrrolidone, etc., and one or more of them are used. A mixture of or the like may be used.

(Anionic surfactant)
The anionic surfactant (foaming anionic surfactant) functions as a foaming agent for the aqueous liquid medium. In addition, when the anionic surfactant is insolubilized, for example, it is insolubilized in the dispersion medium by reaction with a metal cation described later (this will be described later).

  Specific examples of the anionic surfactant include sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate soap, castor oil potassium soap, coconut oil potassium soap, lauroyl sarcosine sodium, Myristoyl sarcosine sodium, oleyl sarcosine sodium, cocoyl sarcosine sodium, coconut oil alcohol sodium sulfate, polyoxyethylene lauryl ether sodium sulfate, sodium alkylsulfosuccinate, sodium lauryl sulfoacetate, sodium dodecylbenzene sulfonate, sodium α-olefin sulfonate etc. In particular, sodium alkyl sulfosuccinate is preferred.

  Here, in order to facilitate dispersion of the anionic surfactant used in the present embodiment in the aqueous liquid medium, the HLB is preferably 10 or more, more preferably 20 or more, and 30 It is particularly preferable that the above is true.

・ HLB
In the present invention, the HLB value means a hydrophilic-hydrophobic balance (HLB) value, which is determined by the Oda method. How to determine the HLB by the Oda method is described in “Introduction to New Surfactants”, pp. 195 to 196 and March 20, 1957, published by Tatsuhiro Oda, “A synthesis of surfactants and its application”, No. 492. It is described on page 502, and it can be determined by HLB = (inorganic / organic) × 10.

  Here, the anionic surfactant according to the present embodiment is a component that is initially dissolved in the dispersion medium when the anionic surfactant is insolubilized, but is insolubilized in the dispersion medium (for example, Become a component which is insolubilized in the dispersion medium by reaction with metal cations. The means for insolubilizing such anionic surfactants is not particularly limited, but together with the anionic surfactants, metal cation sources, acid colloid liquids of melamine-formaldehyde condensates, coagulants such as vinyl phenol polymers, etc. It can be illustrated that it mixes. By insolubilizing the anionic surfactant, it is possible to form a resin foam having a fine and uniform cell structure without limiting the types of the water dispersible resin and the dispersing agent as the main agent. Furthermore, since the anionic surfactant is insolubilized, it becomes difficult to be extracted by water etc. (ie, it becomes possible to prevent bleeding). In addition, since the strong gelation strength is obtained, the cells are stabilized by strongly suppressing the cell unification at the foaming stage, and it becomes possible to form a thick foam (further, the adjustment process). High speed becomes possible). Here, the insolubilization of the anionic surfactant by the combination of the particularly preferable metal cation source is described in detail.

(Metal cation source)
The metal cation source according to the present embodiment is a component capable of releasing metal cation capable of forming a water-insoluble salt in water by combining it with an anionic surfactant. The presence of such components in the system combines with the anionic surfactant to form a water-insoluble salt. As a result, by imparting thixotropy to the foam raw material mixture in which the gas is mixed to reduce fluidity, it is possible to suppress cell coalescence even at the time of heating. Such a metal cation source is not particularly limited as long as it is a component that dissolves in water to generate a metal ion, and metal salts such as inorganic metal salts and organic metal salts such as calcium nitrate; alkalis such as water Calcium oxide or calcium oxide; a simple metal such as calcium. Of these, metal salts are preferred because of their relatively large ionization constants in water.

  Examples of the component include alkali metal ions such as lithium ion, sodium ion and potassium ion, and aluminum ion, barium ion, calcium ion, copper ion, iron ion, magnesium ion, manganese ion, nickel ion, tin ion, titanium ion, Multivalent metal ions such as zinc ions, inorganic acids (eg, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, nitric acid, phosphoric acid, thiocyanic acid, etc.) and organic acids (eg, acetic acid, boric acid, lactic acid, And salts thereof with organic carboxylic acids such as fumaric acid, fumaric acid, citric acid, salicylic acid and benzoic acid, and organic sulfonic acids).

  Specific examples include lithium chloride, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, sodium sulfate, potassium nitrate, sodium acetate, sodium acetate, potassium borate, sodium citrate, potassium benzoate and the like. Salts of alkali metals, and aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, sodium aluminum sulfate, potassium aluminum sulfate, aluminum acetate, barium chloride, barium bromide, barium iodide, barium iodide, barium oxide, barium nitrate, thiocyanate Barium acid, calcium chloride, calcium bromide, calcium iodide, calcium nitrite, calcium nitrate, calcium dihydrogen phosphate, calcium thiocyanate, calcium benzoate, calcium acetate, salicylic acid Calcium tartrate, calcium lactate, calcium fumarate, calcium citrate, copper chloride, copper bromide, copper sulfate, copper nitrate, copper acetate, iron chloride, iron bromide, iron iodide, iron iodide, iron sulfate, iron nitrate, oxalate Iron, iron lactate, iron fumarate, iron citrate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium lactate, manganese chloride, manganese sulfate, manganese nitrate, manganese dihydrogen phosphate , Manganese acetate, manganese salicylate, manganese benzoate, manganese lactate, nickel chloride, nickel bromide, nickel sulfate, nickel nitrate, nickel acetate, tin acetate, tin sulfate, titanium chloride, zinc chloride, zinc bromide, zinc sulfate, zinc nitrate, thiocyanate And salts of polyvalent metals such as zinc acid and zinc acetate.

  In a system in which a stable dispersion type water dispersible resin is present, among components in which a metal cation source of metal cations is a water-soluble metal salt, the gelation strength is strong and the gelation time is short. 100 g water or more is preferable, 30 g / 100 g water or more is more preferable, and 100 g / 100 g water or more is particularly preferable. Examples of the electrolyte that is such a component include calcium nitrate (solubility 138 g / 100 g water), aluminum sulfate (solubility 38.6 g / 100 g water), magnesium sulfate (solubility 36.3 g / 100 g water), etc. .

  In a system in which an unstable dispersion type water dispersible resin is present, foreign matter such as aggregates are less likely to be generated even if the component serving as a metal cation source of metal cations is a poorly water-soluble metal salt, so the solubility is 10 g / 100 g Less than water is preferred, less than 3 g / 100 g water is more preferred, and less than 1 g / 100 g water is particularly preferred. The lower limit is not particularly limited, but is 0.0001 g / 100 g water or more. As an electrolyte which is such a component, for example, calcium citrate (solubility 25.9 mg / 100 g water), calcium carbonate (solubility 0.81 g / 100 g water), monobasic calcium phosphate (solubility 1.8 g / 100 g water), Etc.

(Water soluble polymer)
The water-soluble polymer used in the present embodiment is a polymer having a solubility of 1 g / 100 g water or more. In addition, as a water-soluble polymer, hydrophilic groups such as -COOM group, -SO ₃ M group, (where M represents a hydrogen atom, periodic table I, II, III group element, amine, ammonium)-NH ₂ , -OH, etc. The polymer which has group can be illustrated. As the water-soluble polymer, a sulfonyl group-containing polymer and a carboxyl group-containing polymer are suitable, but compared to the carboxyl group, the functional groups are less likely to crosslink with each other in the multivalent electrolyte aqueous solution, The sulfonyl group-containing polymer is more preferable because the ion concentration difference is increased by the high acid dissociation constant, and high water absorption can be expected. The water-soluble polymer is particularly preferably a copolymer of a sulfonyl group-containing polymer and a carboxyl group-containing polymer.

Specific examples of such water-soluble polymers include diene-based rubbers obtained by copolymerizing (meth) acrylic acid and a diene compound in addition to general purpose resins such as polyvinyl alcohol (PVA) and carboxymethyl cellulose, and maleic anhydride in modified liquid polybutadiene, and particularly effective as the skeleton -COOM, _-SO 3 M (M is a hydrogen atom, the periodic table I, II, III group element, amine, shows the ammonium) a 50 to 50,000 was equivalent / 10 6 ^g with polymer, the periodic table I, as a group II element, sodium, potassium, alkali metals such as lithium, calcium, alkaline earth metals such as magnesium, boron, and aluminum.

Further, as the water-soluble polymer, specifically, -COOM group or -SO ₃ M group containing polyurethane, -COOM group or -SO ₃ M group containing polyurethane, -COOM group or -SO ₃ M group containing polyester, -COOM group Or -SO ₃ M group-containing epoxy compound, -COOM group or -SO ₃ M group-containing polyamic acid, -COOM group or -SO ₃ M group-containing acrylonitrile-butadiene copolymer, -COOM group or -SO ₃ M group-containing styrene- Butadiene copolymer, -COOM group or -SO ₃ M group containing polybutadiene, polyacrylamide, sodium polyacrylate, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (MRC), methyl cellulose (MC), polyethylene oxide And polyethylenimine, and the compound derivative etc. can be used, However, It is not limited to these.

  In addition, as a compound used in order to neutralize at least one part of the carboxyl group contained in the said water-soluble polymer or a sulfonic acid group, the hydroxide of alkali metals, such as sodium hydroxide, lithium carbonate, potassium carbonate , Alkali metal carbonates such as sodium carbonate, alkali metal alkoxides such as potassium t-butoxide and sodium methoxide, hydroxides of polyvalent metals such as calcium hydroxide, magnesium hydroxide and aluminum hydroxide, aluminum isopropoxide Such as polyvalent metal alkoxides, tertiary amines such as triethylamine and tri n-propylamine, diethylamine, secondary amines such as di-n-propylamine, primary amines such as n-propylamine, morpholine and the like Cyclic amines, N, N-dimethylamino Chill (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate such as an amino group-containing (meth) acrylate, ammonium carbonate, ammonium salts, and the like. These may be used alone or in combination of two or more.

Incidentally, the water-soluble polymer has an ethylenically unsaturated group such can act as a polyoxyalkylene chain may have, also cross-linking agent as a hydrophilic portion in addition to -COOM groups or -SO 3 _M group May be In the embodiment, as the water-soluble polymer, in addition to the water-soluble polymer, for example, a polymer having a hydrophilic group such as a hydroxyl group or an amine group and / or a polyoxyalkylene chain may be used in combination.

  The water-soluble polymer preferably has a solubility of 1 g / 100 g water or more, and more preferably 10 g / 100 g water or more, in order to express high water absorbency. The upper limit value is not particularly limited, but is, for example, 500 g / 100 g water or less. The water-soluble polymer preferably has a weight average molecular weight of 500 or more and 1,000,000 or less, more preferably 1000 or more and 100000 or less, and even more preferably 1000 or more and 10000 or less. It is particularly preferable that the number is 5000 or less. By setting it as such a range, high water absorption is expressed, and the rise in liquid viscosity at the time of foaming can be suppressed.

Here, in the present embodiment, the "weight average molecular weight" indicates a numerical value obtained by gel permeation chromatography (GPC). Specifically, the molecular weight distribution of the water-dispersible resin was measured by a GPC measurement device (HLC-8320GPC EcoSEC, manufactured by Tosoh Corporation). As a column, TSKgel SuperMultipore HZ-M (manufactured by Tosoh Corporation) was used. The column is stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) as a solvent is flowed through the column at this temperature at a flow rate of 1 ml / min to prepare a sample concentration of 0.05 to 0.6 wt% It measured by inject | pouring 50-200 microliters of sample solutions. In the measurement of the weight average molecular weight Mw and the number average molecular weight Mn, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of the calibration curve and the count number prepared by several types of monodispersed polystyrene standard samples. As a standard polystyrene sample for preparation of a standard curve, for example, Pressure Chemical Co. Or a molecular weight of 6 × 10 ² , 2.1 × 10 ² , 4 × 10 ² , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , manufactured by Toyo Soda Industry Co., Ltd. Those of 9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ and 4.48 × 10 ⁶ were used. Moreover, RI (refractive index) detector was used for the detector.

(Cross-linking agent for water-soluble polymer)
By using a crosslinking agent for a water-soluble polymer, by causing the water-soluble polymer to be grafted to the water-dispersible resin, the drop of the water-absorbing agent is suppressed and the repeated resistance is improved.

  Such a water-soluble polymer crosslinking agent is not particularly limited, and can be appropriately changed according to the water-soluble polymer to be used, and an organic zirconium compound, an organic titanium compound or a formaldehyde resin (formalin) which crosslinks an oxygen atom such as a carboxyl group And condensation resins) and water-soluble epoxy resins which crosslink nitrogen atoms such as amino groups.

(Gelled component)
Even if the resin foam 110 according to the present embodiment contains a gelling component (a component that causes the aqueous liquid medium to be gelled in order to prevent cell coalescence of the foam-formed aqueous liquid medium in the foaming step described later). Good. Such a gelling component may be appropriately added according to the gelling method, for example, sodium fluorosilicate, potassium fluorosilicate, hexafluorosilicate such as calcium fluorosilicate; or acetate of cyclohexylamine, A cyclohexylamine salt such as a sulfamate salt can be used, and generally, a liquid obtained by converting these compounds into an aqueous solution is used. For example, use of sodium silicofluoride facilitates reaction control such as control of gelation start time.

(Other additives)
As other additives, surfactants (emulsifiers) for water-dispersible resin dispersion, curing agents and the like may be added.

· Surfactant for water dispersible resin dispersion The surfactant for water dispersible resin dispersion according to the present embodiment is a surfactant for dispersing a water dispersible resin (unlike anionic surfactants, It does not have to have the effect as a foaming agent). Such surfactant may be appropriately selected according to the water dispersible resin to be selected. For example, when the water dispersible resin is a urethane emulsion, and when it is an acrylic emulsion, the specific surfactant for water dispersible resin dispersion in the case of a rubber latex is as described above.

-Curing agent The curing agent according to the present embodiment is a crosslinking agent for a water-dispersible resin, and may be added in a necessary amount according to the application and the like. Examples of the curing method using a curing agent include physical crosslinking, ionic crosslinking, and chemical crosslinking, and the crosslinking method can be selected according to the type of water-dispersible resin.

  As the curing agent, it is possible to select the kind and amount of functional groups contained in the resin compounding system that uses epoxy curing agent, melamine curing agent, isocyanate curing agent, carbodiimide curing agent, oxazoline curing agent, etc. You can use an appropriate amount according to your needs.

  When a rubber latex is used as the water dispersible resin, a crosslinking agent (an additive for crosslinking rubber polymers, for example, a vulcanizing agent) commonly used in the production of a resin foam, a crosslinking accelerator (a crosslinking agent) It is an additive for promoting the crosslinking reaction by the crosslinking agent, and for example, a vulcanization accelerator), an antiaging agent, etc. may be added.

  As a crosslinking agent, sulfur, an organic peroxide, a phenol compound, etc. are used according to the kind of rubber polymer, and a crosslinking reaction mechanism. In the case of crosslinking by sulfur, in addition to colloidal sulfur and finely powdered sulfur, sulfur dichloride and sulfur compounds such as dipentamethylenethiuram tetrasulfide can be used. In the case of crosslinking with organic peroxides, hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; acyl peroxides such as benzoyl peroxide and m-toluyl peroxide; t-butyl cumyl peroxide, dicumyl peroxide, 2,5- Alkyl peroxides such as dimethyl-2,5-bis (t-butoxyperoxy) hexane; peroxy esters such as t-butoxyperoxy-3,3,5-trimethylcyclohexanoate, t-butoxyperoxybenzoate; 1,1- Peroxyketals such as bis (t-butoxyperoxy) cyclohexane and 1,1-bis (t-butoxyperoxy) -3,3,5-trimethylcyclohexa; t-butoxyperoxyisopropyl carbonate, t-butoxyper Organic peroxides peroxycarbonate such as carboxymethyl-2-ethylhexyl carbonate can be used. The organic peroxide may be blended as it is, or may be adsorbed by being absorbed to an inorganic powder such as molecular sieve, dissolved in a hydrocarbon or a plasticizer, or mixed with an inert liquid such as polydimethylsiloxane. May be used in the formulation. In the case of crosslinking with a phenol compound, an alkyphenol-formaldehyde resin, a sulfurized-p-tert-butylphenol resin, an alkylphenol-sulfide resin and the like can be used. The blending amount of the crosslinking agent varies depending on the type of rubber polymer, the crosslinking mechanism, and the crosslinking agent, but 0.02 to 20 parts by mass is preferable with respect to 100 parts by mass of the rubber polymer in the mixture of rubber latex. 1 to 10 parts by mass is more preferable.

  Although various substances can be used as the crosslinking accelerator, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc dibenzyldithiocarbamate, ethylphenyl are preferred because they lower the swelling property to polar oils. Zinc dithiocarbamates, zinc dithiocarbamates such as zinc N-pentamethylene dithiocarbamate; tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N'-dimethyl-N, N ' Thiphenyls such as diphenylthiuram disulfide, dipentamethylenethiuram tetrasulfide; N, N-diisopropyl-2-benzothialylsulfenamide N-t-butyl- -Benzothiallylsulfenamide, N-cyclohexyl-2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, etc. Sulfenamides; 2-mercaptobenzothiazole and salts thereof (sodium salt, zinc salt, cyclohexylamine salt, dicyclohexylamine salt, etc.), 2- (4'-morpholinodithio) benzothiazole, 4-morpholinyl-2-benzo Thiazolyl disulfide, benzothiazoles such as 2- (N, N-diethylthiocarbamoylthio) benzothiazole; and mixtures thereof are preferred. Among these, zinc dithiocarbamates are more preferable, and zinc dibutyldithiocarbamate is particularly preferable. 0.02-20 mass parts is preferable with respect to 100 mass parts of rubber polymers in the mixture of rubber latex, and, as for the compounding quantity of a crosslinking accelerator, 0.1-10 mass parts is more preferable.

  Examples of anti-aging agents include diphenylamine compounds such as N-phenyl-N '-(p-toluenesulfonyl) -p-phenylenediamine; condensates of aromatic amines and aliphatic ketones; 2-mercaptobenzimidazole and the like Imidazole compounds such as zinc salts; mono-phenolic compounds such as 2,6-di-t-butyl-4-methylphenol; bis-, tris, polyphenol compounds and the like. The blending amount of the antioxidant is preferably 1.0 to 10 parts by mass, and more preferably 2.0 to 6.0 parts by mass with respect to 100 parts by mass of the rubber polymer in the mixture of the rubber latex.

  As for the cross-linking agent, the cross-linking accelerator and the anti-aging agent, in order to improve the dispersibility in the rubber latex, those additives are previously dispersed in water using a dispersant etc. A vulcanizing paste may be prepared and this vulcanizing paste may be added to the rubber latex.

(Combination of suitable raw materials)
Here, as described above, in the case of using a stable dispersion type water dispersible resin as the water dispersible resin by using the gelation method by insolubilizing the anionic surfactant, a water soluble metal salt as a metal cation source of the metal cation It is preferred to use With such a combination, the effects of high gelation strength and short gelation time can be obtained. Similarly, when using a water dispersible resin of unstable dispersion type as the water dispersible resin, it is preferable to use a hardly water-soluble metal salt as a metal cation source of the metal cation. With such a combination, an effect that foreign substances such as aggregates are less likely to be generated can be obtained.

<Composition>
(Blending amount and blending ratio of each raw material)
As a compounding quantity of water dispersible resin (solid content) with respect to a liquid medium, 30-70 mass parts is preferable with respect to 100 mass parts of liquid media. By setting it as such a range, the effect that a stable foam can be shape | molded is acquired.

  As a compounding quantity of anionic surfactant, 1.0-10 mass parts is preferable with respect to 100 mass parts of water-dispersible resin (solid content) in the mixture (water-based liquid medium) of water-dispersible resin, 10 parts by mass is more preferable. By setting it as such a range, it is easy to make it foam appropriately, and the effect that a fine cell structure can be shape | molded is acquired.

  As a compounding quantity of a water-soluble polymer, 0.5-10 mass parts is preferable with respect to 100 mass parts of water-dispersible resin (solid content) in the mixture of water-dispersible resin, and 2-5 mass parts is more preferable. . By setting it as such a range, the effect that high water absorption can be expressed is acquired.

  In the mixture of the water-dispersible resin, the proportion by mass of the water-soluble polymer crosslinking agent / water-soluble polymer is preferably 0.02 to 5, and more preferably 0.1 to 2 or more.

  The compounding amount of the crosslinking agent (hardening agent) is preferably 0.1 to 20 parts by mass, and 1 to 10 parts by mass with respect to 100 parts by mass of the water-dispersible resin (solid content) in the mixture of water-dispersible resins. Is more preferred. When a vulcanizing paste is used as the curing agent, it is preferably 1 to 20 parts by mass, based on 100 parts by mass of the water-dispersible resin (solid content) in the mixture of water-dispersible resins, and 5 to 15 The parts by mass are more preferred. By setting it as such a range, the effect that a foam with a small compressive residual strain can be shape | molded is acquired.

  When the gelling component (gelling agent) is blended, the blending amount thereof is not particularly limited, but about 1 to 10 parts by mass is suitable with respect to 100 parts by mass of the polymer in the mixture of water dispersible resins. When the blending amount of the gelling agent is out of the above range, suitable gelation can not be expressed, that is, it does not gel as a liquid even after a long time passes, or gelation proceeds in a short time to obtain a desired shape. Molding becomes difficult. As a result, specifically, the time (gelling time) required for the completion of gelation becomes too long or too short, so that a suitable resin foam can not be obtained.

  When the anionic surfactant is insolubilized with metal cation (metal cation source) and an electrolyte is used as the metal cation source, the compounding amount of the electrolyte is a water dispersible resin (in the mixture of water dispersible resins ( 1.0-10 mass parts are preferable with respect to 100 mass parts of solid content, and 2-5 mass parts are more preferable. By setting it as such a range, since it becomes suitable gelation intensity | strength and gelation time, the effect that a fine cell structure can be shape | molded is acquired.

  When the anionic surfactant is to be insolubilized by the metal cation (metal cation source), the valence number of the metal cation which is the target component to be insolubilized / the target component to be insolubilized in the water dispersible resin mixture The valence of the anionic surfactant which is the above {it is omitted in the below-mentioned table etc., "valence ratio" [also referred to as "metal cation (metal cation source) / anionic surfactant] etc.} is 0 1 or more is preferable, 0.5 or more is more preferable, and 1.0 or more which is a molar equivalent of valence is especially preferable. By setting it as such a range, since it becomes suitable gelation intensity | strength and gelation time, the effect that a fine cell structure can be shape | molded is acquired.

<Process>
The adjustment process of the resin foam 110 according to the present embodiment includes a raw material preparation step, a stirring / foaming step, a thixotropy imparting step, and a heating step. The respective steps will be described in detail below.
(Raw material preparation process)
At a raw material preparation process, the aqueous liquid medium which is a raw material mixture of a water absorbing resin foam is prepared by mixing each raw material which was demonstrated above. The mixing method in this case is not particularly limited, and for example, it may be mixed while being stirred in a container such as a mixing tank for mixing the respective components.

(Stirring / foaming process)
In the stirring / foaming step, a predetermined foaming gas is added to the aqueous liquid medium obtained in the above-mentioned raw material preparation step, and these are sufficiently mixed to form a large number of bubbles in the aqueous liquid medium (foamed aqueous liquid medium ). The stirring / foaming step is usually carried out by sufficiently mixing the raw material mixture of the liquid water-absorbent resin foam obtained in the raw material preparation step with the gas for foaming using a mixing apparatus such as a mixing head. .

-Foaming gas The foaming gas mixed with the aqueous liquid medium in the stirring and foaming steps forms bubbles (cells) in the water absorbent resin foam 110, and is obtained depending on the mixing amount of the foaming gas. The expansion ratio and the density of the water-absorbent resin foam 110 are determined. In order to adjust the density of the water-absorbent resin foam, the desired density of the water-absorbent resin foam and the volume of the material of the water-absorbent resin foam (for example, a molding die into which the material of the water-absorbent resin foam is injected The weight of the necessary water-absorbent resin foam raw material may be calculated from the internal volume of the above, and the amount of the foaming gas may be determined so that the desired volume can be obtained with this weight. In addition, air is mainly used as a kind of gas for foaming, but in addition, inert gases such as nitrogen, carbon dioxide, helium, argon and the like can also be used.

Foaming Method, Foaming Conditions The foaming method used in the method of preparing the water-absorbent resin foam 110 according to the present invention is not particularly limited as long as it is a method generally used in the production of foams. Mechanical floss (mechanical foaming) methods can be used. The mechanical froth method is a method in which air in the atmosphere is mixed with the aqueous liquid medium to foam by stirring the aqueous liquid medium with a stirring blade or the like. As a stirring apparatus, although the stirring apparatus generally used for a mechanical floss method can be used without a restriction | limiting especially, For example, a homogenizer, a dissolver, a mechanical floss foaming machine etc. can be used. According to this mechanical floss method, by adjusting the mixing ratio of the aqueous liquid medium and air, it is possible to obtain a water absorbent resin foam having a density suitable for various uses.

  The mixing time of the aqueous liquid medium and the air is not particularly limited, but is usually 1 to 10 minutes, preferably 2 to 6 minutes. The mixing temperature is also not particularly limited, but is usually at normal temperature. In addition, the stirring speed in the above mixing is preferably 200 rpm or more (more preferably 500 rpm or more) to make air bubbles finer, and 2000 rpm or less is preferable (800 rpm or less) to smooth discharge of the foam from the foaming machine. More preferred).

Molding The water-based liquid medium (foamed water-based liquid medium) foamed as described above is formed into a sheet or the like adjusted to the desired thickness of the water-absorbent resin foam by a known means such as a doctor knife or doctor roll. It is molded.

(Thicking process)
In the thixotropy-imparting step, a gelled aqueous liquid medium is obtained by using a predetermined gelling method in the aqueous liquid medium obtained in the raw material preparation step. In this thixotropy-imparting step, when a gelling agent is used, the liquid aqueous liquid medium obtained in the raw material preparation step, the gas for foaming and the gelling agent are sufficiently mixed by a mixing device such as a mixing head. It is carried out by doing. The term "gelled aqueous liquid medium" as used herein refers not only to the completely aqueous liquid medium that has completely gelled, but is obtained in the raw material preparation step by the gelling agent added in the thixotropy imparting step. It refers to both a developing aqueous liquid medium and a fully gelled aqueous liquid medium that are gradually gelled from a liquid aqueous liquid medium.

  In addition, upon completion of gelation, the bubbling gas present in the gelled aqueous liquid medium is held as bubbles. The size of the cell determines the cell diameter, since the cell directly becomes the cell of the resin foam 110 finally obtained.

  The gelling method and the foaming method of the aqueous liquid medium are not limited at all, and may be appropriately selected according to the application and the like. For example, a normal temperature gelation method (Dunlop method) using a gelling agent, a freeze coagulation method (Tararay method) without using a gelling agent, a gelation method using an ammine complex (Kaysam method), thermal gelation using a heat sensitive agent A known method such as a method may be used. In addition, as described above, a gelling method may be used in which the anionic surfactant is insolubilized by blending the metal cation source with the anionic surfactant.

  In addition, when adding a metal cation source to the raw material of the resin foam 110, although the timing of addition may be any time, when gelation time is short especially, when using water-soluble salt with high solubility, it adds before foaming. Then, since the amount of gas that can be mixed in by thickening due to gelation decreases and a dense foam is obtained, it is preferable to add it to the foamed aqueous liquid medium after foaming. In addition, when the gelation time is long or when a slow-releasing water-insoluble salt is used, when added after foaming, the fine cell structure can not be formed due to the coalescence of air bubbles, so adding to the aqueous liquid medium before foaming preferable. On the other hand, the process can be simplified by adding a metal cation source to the aqueous liquid medium (before foaming) in advance.

  The insolubilization of the anionic surfactant detailed above gives thixotropy to the system mainly by insolubilizing the anionic surfactant (foaming anionic surfactant) which is a foaming agent after foaming. However, as the insolubilizing step of the anionic surfactant, a method different from this can be considered. As an example, a water-soluble component (for example, a metal cation derived from a foaming anionic surfactant, a component contained in a water-soluble resin, or a component previously contained in a system after foaming) A method of insolubilizing a water-soluble component) can be mentioned. For example, as a method of forming a water-insoluble component using a metal cation derived from a foaming anionic surfactant, it can be realized by adding another component which is combined with the metal cation to be insolubilized. A more preferable example is the method of adding an anionic surfactant other than the anionic surfactant which is a foaming agent. The solubility in water of anionic surfactants is generally determined as follows: polyvalent metal salt {eg, alkaline earth metal salt (eg, calcium salt)} <alkali metal salt (eg, sodium salt) <ammonium or amine salt, It is order. Taking advantage of this property, for example, using a highly water-soluble salt (eg, a sodium salt of a first anionic surfactant) as a foaming anionic surfactant, a foaming anionic surfactant can be obtained. A water-soluble cation derived from the foamable anionic surfactant is present in the system while dissolving to ensure foamability. Then, after foaming, a second anionic surfactant (for example, an ammonium salt) that forms a salt that is hardly soluble with the water-soluble cation is added to the system. Here, for example, in the case of the above example, the second anionic surfactant is soluble in water as an ammonium salt, but insoluble in water as an alkali metal salt. By adding such a second anionic surfactant to the system, the second anionic surfactant undergoes cation exchange (for example, ammonium → sodium ion) and changes from water soluble to water insoluble Do. As a result, the flowability of the system decreases, and it becomes possible to adjust a foam having a low cell diameter and the like, as in the embodiment in which the foamable anionic surfactant is insolubilized as described above.

  For example, it is assumed that at least an alkali metal salt (e.g., a sodium salt) is used as the foaming anionic surfactant (other surfactants may be used in combination). In this case, when a long chain fatty acid (for example, carbon number of 16 to 22) ammonium (for example, ammonium stearate etc.) is used as the second anionic surfactant, an alkali metal ion derived from the foaming anionic surfactant ( For example, sodium ion and the long chain fatty acid derived from the second anionic surfactant react, and it becomes possible to precipitate a fatty acid alkali metal salt (for example, sodium salt) as a water-insoluble salt. As the foaming anionic surfactant, use of a medium-chain fatty acid (for example, carbon number 8 to 15) alkali metal salt (for example, sodium dodecanoate etc.) is also assumed (in this case, detailed above) This corresponds to an embodiment of insolubilizing a foaming anionic surfactant). In this case, polyvalent metal ions (for example, calcium ions) are added to the foamed system. Thereby, the polyvalent metal ion and the short chain fatty acid derived from the foaming anionic surfactant react, and it becomes possible to precipitate the fatty acid polyvalent metal salt (for example, calcium salt) as a water-insoluble salt.

  In addition, as an insolubilization process of anionic surfactant, you may combine the method mentioned above suitably.

(Heating process)
In the heating step, the dispersion medium in the formed foamed aqueous liquid medium is evaporated. The drying method in this case is not particularly limited, and for example, hot air drying may be used. Also, the drying temperature and the drying time are not particularly limited, but may be, for example, about 80 ° C. and about 1 to 3 hours.

  Further, in this heating step, the dispersion medium evaporates from the foamed aqueous liquid medium, but the passage when this vapor escapes is communicated from the inside to the outside of the water absorbent resin foam. Therefore, in the water absorbent resin foam 110 according to the present embodiment, since the passage when the water vapor is released remains as an open cell, at least a part of the air bubbles present in the water absorbent resin foam becomes an open cell. Here, when the foaming gas mixed in the stirring / foaming step remains as it is, the resulting water-absorbent resin foam becomes closed cells, and the mixed foaming gas is a vapor in this step. When it is communicated when it comes off, it becomes an open cell in the obtained water-absorbent resin foam. In the present invention, some of the cells in the resin foam may be open cells, and the remaining cells may be closed cells, or all the cells may be open cells.

  When the curing agent / crosslinking agent is added, in the heating step, the crosslinking (curing) reaction of the raw material is advanced and completed. Specifically, the raw materials are crosslinked by the curing agent and the crosslinking agent described above, and a cured water-absorbent resin foam is formed. The heating means in this case is not particularly limited as long as the raw material can be sufficiently heated and the raw material can be crosslinked (hardened). For example, a tunnel heating furnace can be used. Also, the heating temperature and heating time may be any temperature and time that can crosslink (cure) the raw material, for example, 80 to 150 ° C. (particularly, about 120 ° C. is preferable) and about 1 hour. .

  According to the water-absorbent resin foam 110 according to the present embodiment, the foam is formed in such a manner that the water-soluble polymer penetrates into the inside of the foam, and therefore, the water-absorbent capacity (water absorption speed) is excellent. Furthermore, since the water-soluble polymer is partially embedded in the polymer matrix, it is excellent in repeated resistance.

<< Preparation method of SAP carrying sheet >>
Next, a method of preparing an SAP-supporting sheet (thin sheet-like material having SAP as a main component), which is a preferable form of the SAP layer 120, will be described.

  The SAP carrier sheet is obtained, for example, by an air laid method in which a crushed wood pulp and the like are mixed with SAP, a binder is added, and the sheet is formed to obtain an SAP carrier sheet.

  In addition, SAP is supported also by a method of coating a dispersion slurry of SAP (for example, a solution in which SAP and microfibrillated cellulose are dispersed in a mixed solvent of water and ethanol) on a water-permeable sheet such as nonwoven fabric. It can be a sheet.

  In addition, as an SAP support sheet, for example, a large amount of SAP is supported on a raised nonwoven fabric and fixed with a hot melt binder, an emulsion binder, an aqueous fiber, etc. Fibrous SAP is mixed with PET fibers to form a web Obtained by molding, sandwiching the top and bottom of the SAP layer with a water-permeable sheet such as a tissue, or the like.

Specifically, a water absorbent fiber core material manufactured by Gelok Co., USA can be mentioned. This material is obtained by supporting a superabsorbent polymer between two cellulose fiber non-woven fabrics. The water absorption amount of the water absorbent fiber core material is 1,000 to 5,000 g / m ² (0.9% sodium chloride aqueous solution). Moreover, the fabric weight of the nonwoven fabric which is a water-permeable layer which forms front and back is 5-100 g / m < ² >.

[nature]
According to the water absorbing sheet 100 according to the present embodiment, it is difficult for water to remain on the surface side (contact surface with water) or inside the water absorbing resin foam 110 due to the excellent water absorbing power of the water absorbing resin foam 110 (SAP Water rapidly flows to the side of the layer 120). Furthermore, when the water flows down inside the water absorbent resin foam 110, the water is dispersed inside the water absorbent resin foam 110, and the water comes in contact with the SAP layer 130 in a wide area. As a result, it is difficult for the water whose capacity has exceeded in the SAP layer 130 to flow back and overflow on the surface, and the rewet hardly occurs. Since it flows down to the SAP layer 120 without being dispersed in the lateral direction (layer direction of the water absorbent resin foam 110), the SAP layer is saturated by supplying excess water to the SAP layer of a minute area And rewet will occur.

[Use]
The water-absorbent sheet 100 according to the present embodiment has excellent water absorbability and water retention ability regardless of the target moisture, and therefore, can be widely used for applications aiming at water absorption such as diapers and catamenial products.

  Here, in the present invention, "insolubilization" is synonymous with "insolubilization" generally understood in the art, and the dissolution is suppressed by changing the water-soluble component to the water-insoluble component. For example, preferably 10% by mass or more (more preferably 50% by mass or more) of the water-soluble component before being insolubilized is precipitated as the water-insoluble component (eg, preferably of anionic surfactant, 10% by mass or more, more preferably 50% by mass or more is a water-insoluble component root); "water-insoluble salt" indicates a salt having a solubility of 1 g / water 100 g or less; "water-soluble metal "Salt" indicates a metal salt having a solubility of 10 g / water 100 g or more; "water-insoluble metal salt" indicates a metal salt having a solubility of 10 g / water 100 g; "solubility" is 1 atm At 25 ° C, water 10 Indicating g grams of saturated compounds against a (g / 100 g water)

Here, as a manufacturing method of the resin foam which concerns on this invention, following form (A)-(F) may be sufficient.
In the present embodiment (A), an aqueous liquid medium containing a water-dispersible resin as a dispersoid, an anionic surfactant as a foaming agent, and water or a mixture of water and a water-soluble solvent as a dispersion medium is used as a gas. The aqueous liquid medium is foamed by mixing and stirring to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated to evaporate the dispersion medium to produce a water absorbent resin foam. The method is a method for producing a water-absorbent resin foam, wherein the aqueous liquid medium further contains a water-soluble polymer that is soluble in the dispersion medium.
The present embodiment (B) is a method for producing the water-absorbent resin foam of the present embodiment (A), wherein the weight average molecular weight of the water-soluble polymer is 500 or more and 1,000,000 or less.
This form (C) is a manufacturing method of the water-absorbing resin foam of this form (A) or (B) whose said water-soluble polymer is a sulfonyl group containing polymer.
This form (D) is a manufacturing method of the water-absorbing resin foam of this form (A) or (B) whose said water-soluble polymer is a carboxyl group-containing polymer.
The present embodiment (E) is a method for producing a water-absorbent resin foam according to the present embodiment (A) or (B), wherein the water-soluble polymer is a copolymer of a sulfonyl group-containing polymer and a carboxyl group-containing polymer. .
In the present embodiment (F), the water-absorbent resin according to any one of the embodiments (A) to (E), wherein the aqueous liquid medium contains a crosslinking agent for crosslinking the water-dispersible resin and the water-soluble polymer. It is a manufacturing method of foam.

Furthermore, as a manufacturing method of the resin foam which concerns on this invention, following form (1)-(15) may be sufficient.
The present embodiment (1) is an aqueous liquid medium containing a water-dispersible resin as a dispersoid, a foaming anionic surfactant as a foaming agent, and water or a mixture of water and a water-soluble solvent as a dispersion medium. The aqueous liquid medium is foamed by mixing and stirring gas to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated to evaporate the dispersion medium to produce a resin foam. It is a manufacturing method of the resin foam including the thixotropy-imparting process which reduces the fluidity of the foaming aqueous liquid medium after the foaming.
In this embodiment (2), the thixotropy-imparting step is a step of insolubilizing at least a part of the foaming anionic surfactant dissolved in the dispersion medium with respect to the dispersion medium. It is a manufacturing method of the resin foam of 1).
In the present form (3), the step of insolubilizing causes a metal cation which forms a water-insoluble salt with the foaming anionic surfactant to be present in a system, and at least a part of the foaming anionic surfactant and the above It is a manufacturing method of the resin foam of this form (2) which is the process of forming the said water-insoluble salt with at least one part of a metal cation.
The present embodiment (4) is an aqueous liquid medium containing a water-dispersible resin as a dispersoid, a foaming anionic surfactant as a foaming agent, and water or a mixture of water and a water-soluble solvent as a dispersion medium. The aqueous liquid medium is foamed by mixing and stirring gas to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated to evaporate the dispersion medium to produce a resin foam. And by causing a metal cation forming a water-insoluble salt with the foaming anionic surfactant to be present in the system, at least a part of the foaming anionic surfactant and at least a part of the metal cation It is a manufacturing method of the resin foam including the process of forming a water insoluble salt.
The present embodiment (5) is the present embodiment (3) or (4), wherein the water-dispersible resin is a stable dispersion-type water-dispersible resin, and the component serving as a metal cation source of the metal cation is a water-soluble component. Is a method for producing a resin foam.
The present embodiment (6) is the present embodiment (3) or (4), wherein the water-dispersible resin is a water-dispersible resin of unstable dispersion type, and the component serving as a metal cation source of the metal cation is a poorly water-soluble component. The method for producing a resin foam according to
In the present embodiment (7), the thixotropy-imparting step causes the system to include other components that form a water-insoluble component with the water-soluble component present in the foamed liquid medium after the foaming, It is a manufacturing method of the resin foam of this form (1) which is the process of forming the said water-insoluble component by at least one part of another component, and at least one part of the said water-soluble type | mold component.
In the present form (8), the water-soluble component is a metal cation derived from the foaming anionic surfactant, and the other component is different from the foaming anionic surfactant. It is a manufacturing method of the resin foam of this form (7) which is anionic surfactant.
The present embodiment (9) is the method for producing a resin foam according to any one of the embodiments (2) to (8), wherein the water dispersible resin is a urethane emulsion.
The present embodiment (10) is the method for producing a resin foam according to any one of the embodiments (2) to (8), wherein the water dispersible resin is an acrylic emulsion.
The present embodiment (11) is the method for producing a resin foam according to any one of the present embodiments (2) to (8), wherein the water dispersible resin is composed of a rubber latex.
This form (12) is a manufacturing method of the resin foam in any one of this form (1)-(11) whose HLB of the said foaming anionic surfactant is 10 or more.
In the present embodiment (13), the valence number of the metal cation which is the target component to be insolubilized / the valence of the foaming anionic surfactant or the second anionic surfactant which is the target component to be insolubilized. It is a manufacturing method of the resin foam in any one of this form (3)-(6) and (8)-(12) whose number is 0.1 or more.
In the present embodiment (14), the solid content ratio of the foaming anionic surfactant in the aqueous liquid medium is 0.5 or more by mass ratio with respect to the water dispersible resin 100. It is a manufacturing method of the resin foam in any one of (1)-(13).

  Next, the present invention will be described more specifically by Examples and Comparative Examples, but the present invention is not limited by these examples.

[material]
«Water-absorbent resin foam raw material»
First, in the present example and the comparative example, the following raw materials were used as a raw material of the water absorbent resin foam. In the following, the method for determining the stable dispersion type or the unstable dispersion type of the water-dispersible resin (the method for calculating the deposition rate) and the method for measuring the HLB value are in accordance with the above-mentioned methods. The tensile breaking strength was measured by punching a test piece into a No. 2 dumbbell shape in accordance with JIS K6400. The tensile elongation at break was measured by punching a test piece into a No. 2 dumbbell according to JIS K6400. The softening point was measured according to JIS K2207. The viscosity was measured using a single cylindrical rotational viscometer (B-type viscometer) according to JIS K7117. The surface tension was measured by the Wilhelmy method using a surface tension meter (manufactured by Kyowa Kagaku Co., Ltd., ESB-V type). The polymer glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) according to JIS K7121.
<Water-dispersible resin>
・ Water dispersible resin 1
Carbonate urethane emulsion (stable dispersion type water dispersible resin; precipitation rate 0.8%), pH 8, hydrophilic group: sulfonic acid group, solid content 40%, tensile breaking strength 50 MPa, tensile breaking elongation 600%, softening point 200- 220 ° C
・ Water dispersible resin 2
{Acrylonitrile-butadiene rubber latex (unstable dispersion type water dispersible resin; deposition rate 33%), pH 11, solid content 40%, medium-high nitrile, viscosity 300 mPa · s, surface tension 34 mN / m, Tg-12 ° C.
<Anionic surfactant>
・ Anionic surfactant 1 (sodium alkyl sulfosuccinate)
Dispersion medium; water, pH 9.4, solid content 30%, HLB 39.7
・ Anionic surfactant 2 (ammonium stearate)
Dispersion medium; water, pH 11, solid content 30%, HLB 25.5
<Metal cation source>
・ Metal cation source 1 (calcium nitrate)
Solubility 138g / 100g water / metal cation source 2 (calcium citrate)
Solubility 0.0259 g / 100 g water <water-soluble polymer>
・ Water-soluble polymer 1
Acrylic acid / sulfonic acid copolymer, molecular weight 3000, solid content 40%
・ Water-soluble polymer 2
Non sulfonyl group containing polymer, molecular weight 5000, solid content 40%
・ Water-soluble polymer 3
Acrylic acid / sulfonic acid copolymer, molecular weight 8000, solid content 40%
<Cross-linking agent for water-soluble polymer>
Ammonium zirconium carbonate, curing agent, hydrophobic HDI isocyanurate (number of functional groups: 3.5, trimer)
<Vulcanizing paste>
Vulcanizing paste: 10 parts by mass of a vulcanizing agent such as sulfur, zinc oxide, thiazole-based vulcanization accelerator, anti-aging agent, 6 parts by mass of Noxceler MZ, 18 parts by mass of zinc oxide 2 types, 13 parts by mass of aging The inhibitor and 3 parts by mass of the dispersing agent were added to 50 parts by mass of ion exchange water and dispersed in a ball mill for 48 hours to prepare a vulcanized paste.
<Gelling agent>
· Gelling agent 1
Polyether modified silicone oil / gelling agent 2
Sodium silicofluoride

<Foam material 1>
The urethane emulsion of the water-dispersible resin 1 is used as the main agent, and 8.6 parts by mass of the anionic surfactant 1, 3.6 parts by mass of the metal cation source 1, 6.0 parts by mass with respect to 100 parts by mass of the main agent The curing agent and 5.0 parts by mass of the water-soluble polymer 1 were mixed to obtain a foam raw material 1.
<Foam raw material 2-10>
A foam raw material was prepared in the same manner as the foam raw material 1 except that the raw materials shown in Tables 1 and 2 were blended.
<Foam material 11-14>
A foam raw material was prepared in the same manner as the foam raw material 1 except that the water-soluble polymer was not added to the foam raw material 1 and the raw materials shown in Table 3 were blended.

«Base material»
The following were used as a base material which carries a foam.
<Base 1>
A superabsorbent polymer layer, 60% by weight, was laminated on a PET film (0.012 mm) between 40% by weight of a cellulose fiber non-woven fabric of two SAP sheets (5240-72, made by elok, USA) 0.3 mm in thickness, Laminated body of 12 g / m ² in basis weight and continuously molded <base material 2>
SAP sheet (made by Gelok Inc., 5240-72, USA) A superabsorbent polymer layer between two 40% by weight cellulose fiber non-woven fabrics, a thickness of 0.3 mm with a 60% by weight laminated, and a continuous weight of 12 g / m ² Laminate of <Base Material 3>
PET film (0.038 mm)

[Formation of water-absorbent sheet]
Preparation of Example 1
An inert gas such as air or nitrogen gas is added to the foam raw material 1 to foam (foaming conditions 100 to 1000 rpm), and after casting on the substrate 1, heat treatment (oven or drying furnace) is performed, A water absorbent sheet (water absorbent foam with SAP sheet) according to Example 1 was obtained.
Preparation of Example 2-10
A water absorbent sheet (water absorbent foam with SAP sheet) according to Example 2-10 was obtained in the same manner as Example 1, except that the used foam raw material was changed to foam raw material 2-10.
Preparation of Example 11-20
A water absorbent sheet (water absorbent foam with SAP sheet) according to Example 11-20 was obtained in the same manner as in Example 1-10, except that the base material was changed to the base material 2.
«Comparative Example 1-4»
A water absorbent sheet (water absorbent foam with SAP sheet) according to Comparative Example 1-4 was obtained in the same manner as in Example 1 except that the used foam raw material was changed to foam raw material 11-14.
«Comparative Example 5-12»
A water-absorbent sheet according to Comparative Example 5-12 was obtained in the same manner as in Example 1-10, except that the base material was changed to the base material 3.
«Comparative Example 13-15»
It is only the base material (base material 1, base material 2 or base material 3) itself.

[Evaluation test]
Next, evaluation of the water absorbing sheet (Examples 1 to 20 and Comparative Examples 1 to 21) was performed. The results are shown in Tables 4-9.
«Rewet property 1»
Instantly insert 10 ml of 0.9% aqueous sodium chloride solution using a 1-inch-diameter tube on the resin foam side of the water-absorbent sheet and wait 10 minutes (remove all the aqueous sodium chloride solution and remove the tube). Then place filter paper on the sample and load 1553 g weight for 2 minutes. The change in weight of the filter paper before and after the test was calculated and evaluated as follows.
When the weight change is less than 0.6 g "◎"
When the weight change is less than 0.8 g "○"
When the weight change is less than 1.0 g "△"
When the weight change is 1.0g or more "×"
«SAP slippage»
After the Rewet 1 test, it was evaluated whether SAP slipped from the water-absorbent sheet (SAP sheet).
"○" when SAP does not slip
When SAP slips a little "△"
When SAP slips a lot "x"
«Rewet property 2»
Place a plate with holes on the resin foam side of the water-absorbent sheet, insert a tube, and use a pump to flow artificial blood at a flow rate of 1.6 ml / min for 3 minutes. Remove the plate after 2 minutes and wipe the blood on the plate with filter paper. After 2 minutes, place another filter paper on the sample and place a 2 kg weight for 1 minute. The weight change before and after the test of all filter papers was calculated and evaluated as follows.
When the weight change is less than 0.6 g "◎"
When the weight change is less than 0.7 g "○"
When the weight change is less than 0.8 g "△"
When the weight change is 0.8g or more "x"

[Reference Example 1]
Next, the present invention will be more specifically described by way of reference examples and reference comparative examples, but the present invention is not limited by these examples.

«Raw material»
First, the following raw materials were used in the present reference example and the reference comparative example. In the following, the method for determining the stable dispersion type or the unstable dispersion type of the water-dispersible resin (the method for calculating the deposition rate) and the method for measuring the HLB value are in accordance with the above-mentioned methods. The tensile breaking strength was measured by punching a test piece into a No. 2 dumbbell shape in accordance with JIS K6400. The tensile elongation at break was measured by punching a test piece into a No. 2 dumbbell according to JIS K6400. The softening point was measured according to JIS K2207. The viscosity was measured using a single cylindrical rotational viscometer (B-type viscometer) according to JIS K7117. The surface tension was measured by the Wilhelmy method using a surface tension meter (manufactured by Kyowa Kagaku Co., Ltd., ESB-V type). The polymer glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) according to JIS K7121.
<Water-dispersible resin>
・ Water dispersible resin 1
Carbonate urethane emulsion (stable dispersion type water dispersible resin; precipitation rate 0.8%), pH 8, hydrophilic group: sulfonic acid group, solid content 40%, tensile breaking strength 50 MPa, tensile breaking elongation 600%, softening point 200- 220 ° C
・ Water dispersible resin 2
{Acrylonitrile-butadiene rubber latex (unstable dispersion type water dispersible resin; deposition rate 33%), pH 11, solid content 40%, medium-high nitrile, viscosity 300 mPa · s, surface tension 34 mN / m, Tg-12 ° C.
<Anionic surfactant>
・ Anionic surfactant 1 (sodium alkyl sulfosuccinate)
Dispersion medium; water, pH 9.4, solid content 30%, HLB 39.7
・ Anionic surfactant 2 (ammonium stearate)
Dispersion medium; water, pH 11, solid content 30%, HLB 25.5
<Metal cation source>
・ Metal cation source 1 (calcium nitrate)
(Solubility 138 g / 100 g water)
・ Metal cation source 2 (calcium citrate)
Solubility 0.0259 g / 100 g water <water-soluble polymer>
・ Water-soluble polymer 1
Acrylic acid / sulfonic acid copolymer, molecular weight 3000, solid content 40%
・ Water-soluble polymer 2
Non sulfonyl group containing polymer, molecular weight 5000, solid content 40%
・ Water-soluble polymer 3
Acrylic acid / sulfonic acid copolymer, molecular weight 8000, solid content 40%
・ Water-soluble polymer 4
Acrylic acid / sulfonic acid copolymer, molecular weight 60000, solid content 40%
<Cross-linking agent for water-soluble polymer>
Zirconium ammonium carbonate <hardening agent>
・ Curing agent Hydrophobic HDI isocyanurate (number of functional groups: 3.5, trimer)
<Vulcanizing paste>
・ Vulcanizing paste 1
Sulfur, zinc oxide, thiazole-based vulcanization accelerator, 10 parts by mass of a vulcanizing agent such as anti-aging agent, 6 parts by mass of Noxceler MZ, 18 parts by mass of zinc oxide 2 types, 13 parts by mass of anti-aging agent, and 3 A part by mass of the dispersant was added to 50 parts by mass of ion exchange water and dispersed by a ball mill for 48 hours to prepare a vulcanized paste.
<Gelling agent>
· Gelling agent 1
Polyether modified silicone oil / gelling agent 2
Sodium silicofluoride

«Formation of water-absorbent resin foam»
<Reference Example 1-1>
(Raw material preparation process)
The urethane emulsion of the water-dispersible resin 1 is used as a main agent, and 8.6 parts by mass of the anionic surfactant 1, 2.4 parts by mass of the inorganic electrolyte 1, 6.0 parts by mass of 100 parts by mass of the main agent A curing agent, 5.0 parts by mass of water-soluble polymer 1, and 1.0 parts by mass of a crosslinking agent for water-soluble polymer were mixed to obtain a resin foam raw material.
(Stirring process)
An inert gas such as air or nitrogen gas was added to the resin foam raw material to foam (foaming conditions: 100 to 1000 rpm).
(Metal cation source addition process)
8.6 parts by mass of the metal cation source 1 was blended with 100 parts by mass of the main agent.
(Heating process)
The resin foam was created by heat-processing (processing conditions oven or drying furnace etc.).
Preparation of Reference Example 1-2 to Reference Example 1-11
A resin foam was produced in the same manner as in Reference Example 1-1 except that the raw materials shown in Tables 10 to 12 were blended.
<Preparation of Reference Example 1-12 to Reference Example 1-13>
A resin foam was produced in the same manner as in Reference Example 1 except that the gelling agents (gelling agent 1 and gelling agent 2) were blended and no metal cation source was added.

<Reference Comparative Example 1-1>
As shown in Table 12, a foam is similarly prepared except that the water-soluble polymer and the crosslinking agent for water-soluble polymer are not added to Reference Example 1-12, and the water-soluble polymer 1 is further sprayed with an air gun. Thus, a water-absorbent resin foam was obtained.
Reference Comparative Example 2
A foam is similarly prepared except that the water-soluble polymer and the crosslinking agent for the water-soluble polymer are not added to Reference Example 1-12, and the water-absorbent resin foam is further impregnated by impregnating the water-soluble polymer 1. And

«Water absorption test»
The water absorption time was measured according to the method described below, and from the measurement results, the water absorption speed and the water absorption were evaluated.
<Test method 1>
One drop (0.033 ml) of ion-exchanged water was dropped on the test piece, and the time until it completely penetrated was measured. The measurement location was measured at a total of 5 points at the four corners and the center of the 5 cm × 5 cm resin foam, and the water absorption speed was evaluated based on the following criteria. In the following evaluations, those with an evaluation of ◎, 、, 及 び and 良好 were good as the evaluation of the water absorption rate in the present invention, and it was judged that the water absorbability was good, and those with an evaluation of × in the present invention It was judged that it was a poor thing as evaluation of a water absorption speed, and it does not have water absorbency.
When the water absorption time for all five measurement points was within 10 seconds "◎"
When the water absorption time is within 10 seconds at 1 to 4 points out of 5 points measured "○"
When the water absorption time is less than 10 seconds and 30 seconds or less at 1 to 4 points out of 5 measurement points “△”
When the water absorption time is less than 30 seconds and 60 seconds or less at 1 to 4 points out of 5 points measured "▲"
When the water absorption time for all 5 measurement points is over 60 seconds "x"
<Test method 2>
Further, the water absorption test was repeated. A fully automatic washing machine (manufactured by Toshiba Corporation, AW-421S) is prepared, the washing water amount is set to 45 L, and the test pieces prepared above (Reference Examples 1-1 to 1-13, Reference Comparative Example 1-1) I put 1-2). After performing a washing process of washing for 13 minutes and dehydration for 7 minutes, the test piece was dried. In order to evaluate the durability (whether or not the water absorbability can be maintained) of the test piece, the water absorbency of the product obtained by repeating the washing step once was evaluated. The obtained results are shown in each table. The water absorption evaluation method is as described above.
Moreover, the durability of the test pieces (Reference Examples 1-1, 1-7, 1-9, 1-11, Reference Comparative Examples 1-1, 1-2) was evaluated by repeatedly performing the washing test. The water absorbency of the product before washing and the product obtained by repeating the washing step 1 to 3 times was evaluated, and the obtained results are shown in Table 13. The water absorption evaluation method is as described above.

  As shown in Table 13, the resin foam of Reference Example 1-1 containing an appropriate amount of a crosslinking agent for a water-soluble polymer maintained very good water absorbability even after three washing steps. From this, it was found that the addition of a suitable amount of crosslinking agent strengthens the bonding between the water-soluble polymer and the resin polymer, suppresses the dropout of the water-soluble polymer, and allows the resin foam to maintain high water absorption for a long time. Moreover, the resin foam of the reference example 1-9 with few addition amounts of the crosslinking agent for water-soluble polymers had the water absorption rate somewhat reduced after one washing process. Furthermore, in the resin foam of Reference Example 1-11 in which the addition amount of the crosslinking agent for water-soluble polymer was small, the water absorption decreased slightly after one washing step, and the water absorption decreased after two washing steps. From this, it was found that, even though a small amount of the water-soluble polymer crosslinking agent is added, the dropout of the water-soluble polymer is suppressed to some extent, but the effect is inferior to the case where an appropriate amount is added. On the other hand, in Reference Comparative Example 1-1 in which the water-soluble polymer was sprayed, and Reference Comparative Example 1-2 in which the water-soluble polymer was impregnated, the water absorbability was greatly reduced after one washing step. From this, when the crosslinking agent for water-soluble polymer is not added, the water-soluble polymer is easily detached, and high water absorption is maintained for a long time as compared with the one in which the crosslinking agent for water-soluble polymer is added. I found it difficult. Similarly, Reference Example 1-7 in which the water-soluble polymer cross-linking agent was not added decreased in water absorbability after the washing process, but had a certain degree of water absorbability even after the three washing processes. .

[Reference Example 2]
Furthermore, although a reference example and a reference comparative example are explained, the present invention is not limited at all by these examples.

«Raw material»
First, in the following reference examples and reference comparative examples, the following raw materials were used. In the following, the method for determining the stable dispersion type or the unstable dispersion type of the water-dispersible resin (the method for calculating the deposition rate) and the method for measuring the HLB value are in accordance with the above-mentioned methods. The tensile breaking strength was measured by punching a test piece into a No. 2 dumbbell shape in accordance with JIS K6400. The tensile elongation at break was measured by punching a test piece into a No. 2 dumbbell according to JIS K6400. The softening point was measured according to JIS K2207. The viscosity was measured using a single cylindrical rotational viscometer (B-type viscometer) according to JIS K7117. The surface tension was measured by the Wilhelmy method using a surface tension meter (manufactured by Kyowa Kagaku Co., Ltd., ESB-V type). The polymer glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) according to JIS K7121.
<Water-dispersible resin>
・ Water dispersible resin 1
Carbonate urethane emulsion (stable dispersion type water dispersible resin; precipitation rate 0.8%), pH 8, hydrophilic group: sulfonic acid group, solid content 40%, tensile breaking strength 50 MPa, tensile breaking elongation 600%, softening point 200- 220 ° C
・ Water dispersible resin 2
Acrylic emulsion (stable dispersion type water dispersible resin; precipitation rate 4.9%), pH 610, solid content 40%, tensile breaking strength 25 MPa, tensile breaking elongation 300%, softening point 100-120 ° C
・ Water dispersible resin 3
Carbonate urethane emulsion (stable dispersion type water dispersible resin; precipitation rate 0.8%), pH 8, hydrophilic group; carboxyl group, solid content 40%, tensile breaking strength 20 MPa, tensile breaking elongation 700%, softening point 170-200 ° C
・ Water dispersible resin 4
Ether-based urethane emulsion (stable dispersion type water dispersible resin; deposition rate 1.1%), pH 8, solid content 40%, tensile breaking strength 20MPa, tensile breaking elongation 500%, softening point 200-220 ° C
・ Water dispersible resin 5
Acrylonitrile-butadiene rubber latex (unstable dispersion type water dispersible resin; precipitation rate 33%), pH 11, solid content 40%, medium-high nitrile, viscosity 300 mPa · s, surface tension 34 mN / m, Tg-12 ° C.
・ Water-dispersible resin 6
Styrene-butadiene rubber latex (unstable dispersion type water dispersible resin; precipitation rate 38%), pH 10, solid content 40%, viscosity 440 mPa · s, surface tension 32 mN / m, Tg-63 ° C
・ Water dispersible resin 7
Natural rubber latex (unstable dispersion type water dispersible resin; precipitation rate 35%), pH 10, solid content 40%, viscosity 300 mPa · s, surface tension 34 mN / m, Tg-75 ° C
<Anionic surfactant>
・ Anionic surfactant 1 (sodium alkylsulfosuccinate derived from beef tallow)
Dispersion medium; water, pH 9.4, solid content 30%, HLB 39.7
・ Anionic surfactant 2 (ammonium stearate)
Dispersion medium; water, pH 11, solid content 30%, HLB 25.5
・ Anionic surfactant 3 (potassium oleate soap)
Dispersion medium; water, pH 11.2, solid content 30%, HLB 18.3
・ Anionic surfactant 4 (sodium alkyl diphenyl ether sulfonate)
Dispersion medium; water, pH 8.5, solid content 30%, HLB 9.0
<Metal cation source>
・ Metal cation source 1 (calcium nitrate)
Solubility 138g / 100g Water and metal cation source 2 (aluminum sulfate)
Solubility 38.6g / 100g Water and metal cation source 3 (magnesium sulfate)
Solubility 36.3g / 100g water / metal cation source 4 (calcium citrate)
Solubility 0.0259g / 100g Water and metal cation source 5 (calcium carbonate)
Solubility 0.81g / 100g Water and metal cation source 6 (dibasic calcium phosphate)
Solubility 1.8g / 100g water <hardener>
・ Curing agent Hydrophobic HDI isocyanurate (number of functional groups: 3.5, trimer)
<Vulcanizing paste>
Vulcanizing paste 10 parts by mass of a vulcanizing agent, 6 parts by mass of a thiazole-based vulcanization accelerator, 18 parts by mass of zinc oxide 2 types, 13 parts by mass of an antioxidant, and 3 parts by mass of a dispersing agent Add to parts by mass of ion-exchanged water and disperse in a ball mill for 48 hours to prepare <gelling agent>
· Gelling agent 1
Sodium silicofluoride ・ gelling agent 2
Polyether modified silicone oil <water soluble polymer>
・ Water-soluble polymer acrylic acid / sulfonic acid copolymer, molecular weight 3000, solid content 40%

«Formation of foam»
<Reference Example 2-1>
(Raw material preparation process)
The urethane emulsion of the polymer water dispersion 1 is used as a main agent, and 8.6 parts by mass of the anionic surfactant 1, 2.4 parts by mass of the metal cation source 1, 6.0 parts by mass with respect to 100 parts by mass of the main agent The curing agent 1 was mixed to obtain a resin foam raw material.
(Stirring process)
An inert gas such as air or nitrogen gas was added to the resin foam raw material to foam (foaming conditions: 100 to 1000 rpm).
(Heating process)
The resin foam having a thickness of 1 mm was obtained by heat treatment in an oven, a drying furnace or the like.
(Liquid viscosity after foaming)
The liquid viscosity after foaming was measured at room temperature using a single cylindrical rotational viscometer (B-type viscometer) according to JIS K 7117-1, and was 3000 mPa · s.

Preparation of Reference Examples 2-2 to 2-38 and Reference Comparative Examples 2-1 to 2-8
According to the composition shown to Tables 14-18, it carried out similarly to the reference example 2-1, and obtained the resin foam. In addition, regarding liquid viscosity, it became comparable with the reference example 1 also about the reference examples 2-2 to 2-38 and the reference comparative examples 2-1 to 2-8.

«Evaluation method of resin foam»
Next, according to the following, evaluation of the resin foam which concerns on reference example 2-1 to 2-38 and reference comparative example 2-1 to 2-8 was performed. The results (in particular, the appearance and the distribution of cell diameter) are shown in Tables 14-18.
<Appearance>
The state of the cells and the surface of the resin foam were evaluated visually. When the cell was uniform, it was evaluated as “○”, when the cell was rough, “Δ”, and when the cell was very rough and when the cell was not formed (not foamed), it was evaluated as “x”. 3 is a SEM photograph of the resin foam according to the reference example 2-1, FIG. 4 is a SEM photograph of the resin foam according to the reference example 2-19, and FIG. 5 is a reference comparative example 2- It is a SEM photograph of the resin foam which concerns on 1. FIG.
<Density>
The apparent density was measured at room temperature according to JIS K6400. The test result of Reference Example 2-1 was 150 kg / m ³ . The same results were obtained for Reference Examples 2-2 to 2-38 and Reference Comparative Examples 2-1 to 2-8.
<Distribution of average cell diameter and cell diameter>
A cell photograph of the cross section of the resin foam was taken using a scanning electron microscope (SEM, VHXD-500 manufactured by Keyence Corporation). Thereafter, each cell diameter was measured using image processing software Image-Pro PLUS (manufactured by Media Cybernetics, 6.3 ver). The cell photograph (200 times) of the cross section of the resin foam of the resin foam (thickness 1 mm) obtained in the reference example 2-1 was image | photographed, and each cell diameter was measured with image processing software Image-Pro PLUS. More specifically, first, using a scanning electron microscope (SEM, VHXD-500 manufactured by Keyence Corporation), a cell photograph (200 ×) of a cross section of the resin foam is taken (FIG. 3). Thereafter, the SEM image is read using image processing software Image-Pro PLUS (manufactured by Media Cybernetics, 6.3 ver), and space calibration is performed (FIG. 6). Next, the contrast is adjusted to recognize the cell by contrast (FIG. 7). Next, the shape of the cell is read by image processing {not the perfect circle, but the shape is recognized as it is (FIG. 8)}. Next, "diameter (average)" is selected as a measurement item (FIG. 9). Next, each cell diameter is calculated as a value obtained by measuring the diameter passing through the center of gravity of the object in steps of 2 degrees and averaging them (FIG. 10). As a measurement result, the average cell diameter was 69.8 μm, and the number of cells was 295. Next, when the cell diameter distribution was measured from the obtained values, Sx / S = in the total value S of the cell areas of all the cells and the total value Sx of the cell areas having a cell diameter of 1 to 100 μm. It became 0.52. The same measurement is carried out for the other reference examples and the reference comparative examples as well, and those with Sx / S ≧ 0.3 as “○”, 0.3> Sx / S ≧ 0.1 as “Δ”, 0. 1> It evaluated that the thing of Sx / S was "x". In Reference Example 2-19 (FIG. 4), the average cell diameter size was 71.8 μm, the number of cells was 175, and Sx / S = 0.18. Further, in Reference Comparative Example 2-1 (FIG. 5), the average cell diameter size was 91.2 μm, the number of cells was 37, and Sx / S = 0.06.

100 Water-absorbent sheet 110 Water-absorbent resin foam 120 SAP layer 130 Water-impermeable layer 140 Water-permeable sheet

Claims (6)

A water-absorbent sheet comprising a water-absorbent resin foam layer and a highly water-absorbent resin (SAP) layer,
The water-absorbent resin foam layer is
An aqueous system comprising a water dispersible resin as a dispersoid, an anionic surfactant as a foaming agent, water or a mixture of water and a water-soluble solvent as a dispersion medium, and a water-soluble polymer soluble in the dispersion medium A gas is mixed into the liquid medium and stirred to foam the aqueous liquid medium to obtain a foamed aqueous liquid medium, and the foamed aqueous liquid medium is heated to evaporate the dispersion medium, thereby forming a water absorbent resin foam. Karadadea is,
The water-soluble polymer is a sulfonyl group-containing polymer or a copolymer of a sulfonyl group-containing polymer and a carboxyl group-containing polymer,
A water-absorbent sheet, wherein the highly water-absorbent resin (SAP) layer and the water-absorbent resin foam layer are laminated in this order via another layer . The water-absorbent sheet according to claim 1, wherein the aqueous liquid medium further contains a metal cation source. The water absorbing sheet further comprises a water impermeable layer,
The water-impermeable layer is directly or via another layer on the side of the high water-absorbent resin (SAP) layer opposite to the side laminated with the water-absorbent resin foam layer and the other layer. The water absorbent sheet according to claim 1 or 2, which is laminated. Before Symbol further layer is a water permeable sheet covering the super absorbent polymer (SAP), water absorption sheet according to claim 3, wherein. The water-absorbent sheet according to any one of claims 1 to 4, wherein the other layer is a water-permeable sheet covering the highly water-absorbent resin (SAP). The water absorbent resin foam is
The water-absorbent sheet according to any one of claims 1 to 5 , which is obtained by a method including a thixotropy-imparting step of decreasing the flowability of the foamed aqueous liquid medium after the foaming.

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